In an oil and gas wells, there are occasions when it is desired to set material into a zone of interest within a wellbore. This can be done by lowering what is commonly referred to as a dump bailer into the wellbore on tubing or wireline.
It is well-known in the oil well drilling and production arts to use cement or other materials, for various well operations such as, for example, to seal off a certain formations below a production packer so that other producing zones can be perforated. Typically, the dispensing of cement or other materials into the well bore is done using a device known in the industry as a “dump bailer.” Older conventional dump bailers were gravity operated, using a very large weight which falls under the force of gravity to dispense any contained material into the bore. The problem with these types of device is that they often fail to fully dispense the material as desired requiring multiple trips and additional expense to the well operation.
More modern conventional dump bailers use explosive components to generate pressure to actuate the device and dispense material into the bore. However, premature actuation of the explosive components is of particular concern with downhole devices. Some common sources that can cause premature actuation include careless application of power to cable conductors, stray electrical currents from power generators, cathodic protection systems, lightning or static, and extraneous radio frequency energy. In addition to premature actuation, the misfiring or failure of a downhole explosive component to detonate presents another particular concern. The hazard associated with a misfired device is magnified by the possibility that an operator retrieving the device may not know that the device has not detonated.
The present invention provides an improvement over prior art type dump bailers by providing a dump bailer which uses a surface electrical power source to move a piston, which fully dispenses the cement or other product into the well bore. The use of a surface power supply as described herein is an improvement over prior art type dump bailers which rely upon gravity to pull a piston or dispensing member downwardly, or relies upon the use of an explosive component that generates pressure to move a piston.
Some examples of prior art devices include, U.S. Pat. No. 2,696,258, entitled “Oil Well Cementing Packer,” which discloses a cementing packer wherein a charge is exploded to drive the cement from the bailer. The device uses a vertically elongated container with a body of cement contained in the container. A gas generated charge displaces the cement through a lower outlet in the container into the well bore. The device is further characterized by a bore sealing mechanism which is adapted to expand by cement displacing gases to plug the well bore above the zone being cemented, and thus seal the bore against upward dissipation of the force of the gases.
U.S. Pat. No. 2,591,807, entitled “Oil Well Cementing,” discloses an apparatus for depositing cement in a zone within a well bore. The apparatus further includes a vertically elongated container to be lowered into the well bore zone and containing a body of cement, a relatively high velocity explosive charge in the lower portion of the container and serving upon ignition to cavitate the well bore at the zone. A relatively lower velocity explosive charge in the container above the body of cement serves upon ignition to force cement downwardly and outwardly into the cavity and a fuse for igniting the charges extends first to the high velocity charge and then to the lower velocity charge so as to ignite the charges in that order.
U.S. Pat. No. 3,187,813, entitled “Apparatus for Depositing Cement or the Like in a Well,” provides a tool assembly to be lowered into a well on a flexible line and includes a container having a massive cementitious material therein. An opening is provided at the lower portion of the container which can be opened while in the well and thereby allow cementitious material to flow downwardly from the container and into the well by gravity. The assembly is constructed to avoid the application of the cementitious material with any other displacing forces other than gravity during the downward flow so that the cementitious material after leaving the container may seek its own level in the well by gravity.
U.S. Pat. No. 3,208,521, entitled “Recompletion of Well,” discloses a method of forming a plug in a well pipe including the steps of anchoring a support member at a given level in the pipe, depositing a quantity of liquid cementitious mixture on the support member, inserting a conductive metal rod in the cementitious mixture so that the rod extends substantially through the cementitious mixture and is substantially centrally located on the longitudinal axis of the well pipe. After the cementitious mixture has hardened for at least a period of two hours, an electrical direct current is passed from the well pipe to the rod through the hardened cementitious mixture until there has passed at least fifty coulombs of electricity per square inch of contact between the pipe and the cementitious mixture.
U.S. Pat. No. 2,689,008, entitled “Method for Cementing Well,” provides a method for cementing a well having a perforated casing therein, which comprises locating a body of hydraulic cementitious material in the perforated casing in the region of and adjacent the perforations and locating a high explosive detonating charge in the body of the cementitious material. The charge is discharged and at least a portion of the cementitious material is forced through the perforations thereby dehydrating and setting the portions of cementitious material to seal the perforations.
U.S. Pat. No. 2,725,940, entitled “Dump Bailer for Well,” discloses a dump bailer for wells including a tubular body, a closure for its upper end including an attachment to a lowering cable, a filler opening in the wall of the body adjacent the closure, a tubular sleeve coaxially connected to the lower end of the body, a removable plug closing lower into the sleeve, and the downwardly facing annular shoulder in the bore of the sleeve axially spaced from the plug, the sleeve having a discharge passage through the wall thereof between the shoulder and the plug, a tubular frangible liner is coaxially positioned in the bore of the sleeve opposite the passage and having one end abutting the shoulder and the other end abutting the plug, an annular resilient seal is disposed to form a fluid type seal between the liner and the wall of the sleeve at points above and below the passage thereby to close off the passage. An electrically fired explosive charge positioned in the bore of the liner is provided and the cable provides a means for firing the charge so as to shatter the liner and open the passage.
U.S. Pat. No. 3,379,251, entitled “Dump Bailer,” discloses a dump bailer for depositing material in a well bore. The apparatus includes a reservoir section formed of a length of flexible tubing, a bottom plug closing one end of the reservoir section, a supporting head having a lower portion to which the upper end of the reservoir section is attached, and an upper portion mechanically attaching a wireline cable for positioning the dump bailer in the well bore, and means to fill the reservoir with a material to be deposited. A squeegy is formed of two spaced apart rollers, attached together by crossbars and secured to the upper end of the flexible tubing forming the reservoir section. A pair of pivotally spring loaded fingers are attached to the crossbars for engaging the walls of the bore hole upon any upward movement of the dump bailer so that the squeegy remain stationary and then as the dump bailer is moved upward, the pressure on the bottom of the reservoir is increased ejecting the bottom plug and then positively depositing the material in the reservoir.
U.S. Pat. No. 3,318,393, entitled “Formation Treatment,” describes a wireline apparatus for treating a permeable earth formation zone containing a formation fluid under pressure and traversed by a case bore hole containing a column of fluid extending upwardly of the zone providing a hydrostatic pressure environment within the casing greater than the pressure of formation fluid. The apparatus includes a body adapted to be lowered within the bore hole by means of a wireline, a perforator including explosive material disposed on the body for perforating the casing along a predetermined axis to establish fluid communication with the formation therebeyond when the explosive material is fired, a compartment in the body providing a volume of low pressure gas of a size to contain any gases evolving from the explosive material when fired at a pressure less than the pressure of the formation fluid, a sealing mechanism on the body for isolating the fluid communication from the hydrostatic pressure environment of the bore hole by sealing off an isolated area of the casing wall when urged thereagainst.